ZS Ph2/3 Dose-response Study in Japan

To assess efficacy of 5 g three times daily (TID) and 10 g TID ZS versus placebo in Japanese patients with hyperkalemia (serum potassium [S-K] ≥ 5.1 mmol/L and ≤ 6.5 mmol/L).

Patients not receiving any therapy for hyperkalemia and with 2 consecutive i-STAT potassium values of ≥ 5.1 mmol/L and ≤ 6.5 mmol/L will be enrolled and randomized 1:1:1 to receive ZS 5 g, ZS 10 g, or placebo TID for 48 hours. Throughout the study most potassium values will be measured at fasting before taking study drug. Nothing should be taken by mouth except water, coffee or tea, with or without milk and/or sugar, and essential medications, prior to the blood collection for a minimum of 8 hours. Potassium level should be determined by both i-STAT and the Central Laboratory on all occasions. Treatment decisions (eg, stopping rules) will be made based on i-STAT potassium values, as these provide clinical sites with a real-time measurement. Statistical analyses on the study data will in principle be based on S-K values as measured by the central laboratory. Safety and tolerability will be assessed on an ongoing basis. Standard study assessments including blood potassium, clinical chemistry (including calcium, magnesium, sodium, phosphate, creatinine, bicarbonate, and blood urea nitrogen [BUN]) and hematology parameters, urinalysis, vital signs, physical examinations, and electrocardiograms (ECGs) will be assessed during the study at the time points specified in the assessments schedule. All women of childbearing potential will have a urine pregnancy test prior to enrollment and at their End of Study (EOS) visit. Stopping rules will be implemented to ensure subjects discontinue the study treatment and receive alternative therapy in case of significant hyperkalemia, hypokalemia, or significant cardiac arrhythmias.